Dependecny Injection(DI) to Access EJBs

There are two ways to access the EJBs: 1. JNDI 2. DI

Advantages:

1. Removes JNDI lookups
2. DI can inject this:
   1. @EJB
   2. @Resource, @PersistenceContext, @EntityManager

DI is supported within:

1. Enterprise Java Beans
2. Servlets/JSPs/Filters/Managed Beans/
3. Applicaiton Client Container clients

Annotations:

@EJB

Example of dependency injection EJB -> Servlet

[code language=”java”]
// this is servlet
@WebServlet(name="DICalculator", urlPatterns = {"/DICalculator"})
public class DICalculatorServerlet extends HttpServlet {

// Line below injects RemoteCalculator bean into this servlet
@EJB
private RemoteCalculator calculator;
// now we can use the injected object
int sum = calculator.multiply(5,5);
RequestDispatcher dispatcher = request.getRequestDispatcher("calc-result.jsp");
[/code]

@Resource